Propeller shaft and constant velocity universal joint used therein

BACKGROUND OF THE INVENTION

p-00021. Field of the Invention

p-0003The present invention relates to a propeller shaft and a constant velocity universal joint used therein, which are used in wheeled motor vehicles.

p-00042. Description of the Related Art

p-0005Usually, the propeller shaft for the wheeled motor vehicle has a split construction including a drive shaft that is adapted to connect to an output shaft of a transmission, a driven shaft that is adapted to connect to a differential gear and a coupling device, such as, constant velocity universal joint, Cardin joint or the like, that is operatively disposed between mutually facing ends of the drive and driven shafts. In practical use, an axially middle portion of the propeller shaft is rotatably held by a support device fixed to a body of the vehicle. Furthermore, for holding a grease in the coupling device, there is provided a boot between the drive shaft and the coupling device.

p-0006One of such boots is disclosed by U.S. Pat. No. 7,470,198. The boot disclosed by the patent is generally conical in shape and made of a soft rubber or flexible plastic. A larger diameter outer portion of the boot is secured to an outer cylindrical member of a constant velocity universal joint (viz., coupling device) through an annular metal retainer and a smaller diameter inner portion of the boot is secured to the drive shaft through an annular metal band. With provision of the boot, an interior of the constant velocity universal joint is protected from entry of muddy water, dusts and the like and furthermore a grease in the interior is suppressed from leakage.

SUMMARY OF THE INVENTION

p-0007However, usage of the boot for protecting the interior of the universal joint from entry of foreign matter has the following drawbacks. That is, it often happens that fitting the boot to a desired position of the propeller shaft takes a lot of time due to a complicated fitting process.

p-0008That is, at first, the boot is fixed at its larger diameter outer portion to an outer cylindrical member of the universal joint to produce a semifinished unit of a propeller shaft. Usually, this fitting process is carried out in an automotive component factory. Then, the semifinished unit is transported to a vehicle assembling factory. At this assembling factory, the semifinished unit of propeller shaft is connected to a vehicle body and then the smaller diameter inner portion of the boot is fixed to a drive shaft (viz., output shaft of a transmission).

p-0009As will be understood from the above, such fitting process is troublesome and thus takes a lot of time thereby causing increase in production cost of the vehicle.

p-0010Accordingly, the present invention is provided by taking the above-mentioned drawbacks of the conventional technology into consideration and aims to provide a propeller shaft that is free of the above-mentioned drawbacks.

p-0011In accordance with a first aspect of the present invention, there is provided a propeller shaft which comprises an inner cylindrical member having a center through bore, the center through bore having a splined cylindrical inner wall with which a splined cylindrical outer wall of a shaft is engaged; an outer cylindrical member disposed around the inner cylindrical member; a torque transmitting unit installed between the inner and outer cylindrical members to transmit a torque between the inner and outer cylindrical members; a sleeve member coaxially connected to the center through bore of the inner cylindrical member, the sleeve member permitting passage of the splined cylindrical outer wall of the shaft therethrough before effecting the engagement between the splined cylindrical outer wall of the shaft and the splined cylindrical inner wall of the inner cylindrical member; a boot unit having one end fixed to the outer cylindrical member and the other end fixed to the sleeve member thereby to hermetically close one open side of an interior of the outer cylindrical member, the interior containing therein a grease; and a positioning mechanism that effects a relative axial positioning between the shaft and the inner cylindrical member when the splined cylindrical outer wall of the shaft is inserted through the sleeve member into a given position of the center through bore of the inner cylindrical member.

p-0012In accordance with a second aspect of the present invention, there is provided a propeller shaft which comprises an inner cylindrical member having a center through bore, the center through bore having a splined cylindrical inner wall with which a splined cylindrical outer wall of a shaft is engaged; an outer cylindrical member disposed around the inner cylindrical member; a torque transmitting unit installed between the inner and outer cylindrical members to transmit a torque between the inner and outer cylindrical members; a sleeve member coaxially connected to the center through bore of the inner cylindrical member, the sleeve member permitting passage of the splined cylindrical outer wall of the shaft therethrough before effecting the engagement between the splined cylindrical outer wall of the shaft and the splined cylindrical inner wall of the inner cylindrical member; a flexible boot unit having one end fixed to the outer cylindrical member and the other end fixed to the sleeve member thereby to hermetically close one open side of an interior of the outer cylindrical member, the interior containing therein a grease; a seal ring arranged between the sleeve member and the shaft to suppress entry of foreign matter into the center through bore of the inner cylindrical member; and a positioning mechanism that effects a relative axial positioning between the shaft and the inner cylindrical member when the splined cylindrical outer wall of the shaft is inserted through the sleeve member into a given position of the center through bore of the inner cylindrical member.

p-0013In accordance with a third aspect of the present invention, there is provided a constant velocity universal joint which comprises an inner cylindrical member having a center through bore, the center through bore having a splined cylindrical inner wall with which a splined cylindrical outer wall of a shaft is engaged; an outer cylindrical member disposed around the inner cylindrical member; a torque transmitting unit installed between the inner and outer cylindrical members to transmit a torque between the inner and outer cylindrical members; a sleeve member coaxially connected to the center through bore of the inner cylindrical member, the sleeve member permitting passage of the splined cylindrical outer wall of the shaft therethrough before effecting the engagement between the splined cylindrical outer wall of the shaft and the splined cylindrical inner wall of the inner cylindrical member; a boot unit having one end fixed to the outer cylindrical member and the other end fixed to the sleeve member thereby to hermetically close one open side of an interior of the outer cylindrical member, the interior containing therein a grease; and a positioning mechanism that effects a relative axial positioning between the shaft and the inner cylindrical member when the splined cylindrical outer wall of the shaft is inserted through the sleeve member into a given position of the center through bore of the inner cylindrical member.

BRIEF DESCRIPTION OF THE DRAWINGS

p-0014Other objects and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings, in which:

p-0015<figref idrefs="DRAWINGS">FIG. 1</figref> is a partially sectioned and partially exploded view of a front assembly of a propeller shaft of a first embodiment of the present invention;

p-0016<figref idrefs="DRAWINGS">FIG. 2</figref> is a view similar to <figref idrefs="DRAWINGS">FIG. 1</figref>, but showing a condition in which an input shaft is properly coupled with a constant velocity universal joint to constitute the front assembly of the propeller shaft of the first embodiment;

p-0017<figref idrefs="DRAWINGS">FIG. 3</figref> is an enlarged sectional view of the part enclosed by a circle indicated by an arrow “A” in <figref idrefs="DRAWINGS">FIG. 2</figref>;

p-0018<figref idrefs="DRAWINGS">FIG. 4</figref> is a side view of an entire construction of the propeller shaft of the first embodiment of the present invention;

p-0019<figref idrefs="DRAWINGS">FIG. 5</figref> is a view similar to <figref idrefs="DRAWINGS">FIG. 2</figref>, but showing an essential part of a front assembly of a propeller shaft of a second embodiment of the present invention;

p-0020<figref idrefs="DRAWINGS">FIG. 6</figref> is a view similar to <figref idrefs="DRAWINGS">FIG. 2</figref>, but showing an essential part of a front assembly of a propeller shaft of a third embodiment of the present invention;

p-0021<figref idrefs="DRAWINGS">FIG. 7</figref> is a view similar to <figref idrefs="DRAWINGS">FIG. 2</figref>, but showing an essential part of a front assembly of a propeller shaft of a fourth embodiment of the present invention;

p-0022<figref idrefs="DRAWINGS">FIG. 8</figref> is a view similar to <figref idrefs="DRAWINGS">FIG. 2</figref>, but showing an essential part of a front assembly of a propeller shaft of a fifth embodiment of the present invention; and

p-0023<figref idrefs="DRAWINGS">FIG. 9</figref> is a view similar to <figref idrefs="DRAWINGS">FIG. 2</figref>, but showing an essential part of a front assembly of a propeller shaft of a sixth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

p-0024In the following, six embodiments <b>1</b><i>a</i>, <b>1</b><i>b</i>, <b>1</b><i>c</i>, <b>1</b><i>d</i>, <b>1</b><i>e </i>and <b>1</b><i>f </i>of the present invention will be described in detail with reference to the accompanying drawings.

p-0025In the following description, various directional terms, such as right, left, upper, lower, rightward and the like are used for ease of explanation. It is however to be noted that such terms are to be understood with respect to only a drawing or drawings on which a corresponding element or portion is shown.

p-0026Referring to <figref idrefs="DRAWINGS">FIGS. 1 to 4</figref>, there is shown a propeller shaft is which is a first embodiment of the present invention.

p-0027As is seen from <figref idrefs="DRAWINGS">FIG. 4</figref>, propeller shaft <b>1</b><i>a </i>comprises an input shaft <b>2</b> of steel that is adapted to connect to an output shaft of a transmission (not shown) mounted on a motor vehicle, a drive shaft <b>4</b> of aluminum alloy that is connected to input shaft <b>2</b> through a first constant velocity universal joint <b>3</b><i>a</i>, a driven shaft <b>6</b> of aluminum alloy that is connected to drive shaft <b>4</b> through a second constant velocity universal joint <b>5</b> and an output shaft <b>8</b> of steel that is connected to driven shaft <b>6</b> through a third constant velocity universal joint <b>7</b> and connected to an input shaft of a differential gear (not shown). As shown, when propeller shaft is practically used, a center bearing <b>9</b> holding an axially given portion of propeller shaft is supported by a vehicle body “VB” through a bracket <b>10</b>. In the illustrated embodiment, center bearing <b>9</b> holds a right end of drive shaft <b>4</b> at a position near second constant velocity universal joint <b>5</b>.

p-0028As is seen from <figref idrefs="DRAWINGS">FIGS. 1 and 2</figref>, input shaft <b>2</b> from the output shaft of a transmission has a stepped right end portion that includes a larger diameter shaft portion <b>11</b> with an annular flat surface <b>11</b><i>a </i>facing rightward, a medium diameter intermediate portion <b>12</b> projected rightward from and integral with larger diameter shaft portion <b>11</b> and a smaller diameter right shaft portion <b>13</b> projected rightward from and integral with medium diameter intermediate portion <b>12</b>.

p-0029As shown in the drawings, medium diameter intermediate portion <b>12</b> is shorter in length than smaller diameter right shaft portion <b>13</b>. A cylindrical outer surface of medium diameter intermediate portion <b>12</b> is formed at an axially middle part thereof with an annular groove <b>12</b><i>a </i>and a seal ring <b>14</b> made of a synthetic rubber is tightly received in annular groove <b>12</b><i>a. </i>

p-0030As shown, a cylindrical outer surface of smaller diameter right shaft portion <b>13</b> is splined, that is, the cylindrical outer surface is formed with a plurality of axially extending splines <b>15</b>. As shown, smaller diameter right shaft portion <b>13</b> has a tapered right end <b>13</b><i>a. </i>

p-0031As is seen from <figref idrefs="DRAWINGS">FIGS. 1 and 2</figref>, an annular groove <b>13</b><i>b </i>is formed around a boundary part between tapered right end <b>13</b><i>a </i>and a major part of smaller diameter right shaft portion <b>13</b>. Annular groove <b>13</b><i>b </i>has a generally rectangular cross section as is seen from <figref idrefs="DRAWINGS">FIG. 3</figref>. A snap ring (or circlip) <b>16</b> is tightly received in annular groove <b>13</b><i>b </i>for the purpose which will be clarified hereinafter.

p-0032Snap ring <b>16</b> is made of a resilient metal and has a generally circular cross section as is seen from <figref idrefs="DRAWINGS">FIG. 3</figref>. Although not shown in the drawings, snap ring <b>16</b> has both ends that are movable relative to each other to vary the diameter of snap ring <b>16</b>.

p-0033As is seen from <figref idrefs="DRAWINGS">FIGS. 1 and 2</figref>, first constant velocity universal joint <b>3</b><i>a </i>is of a fixed type and comprises an outer cylindrical member <b>17</b> that has a right end connected to drive shaft <b>4</b>, an inner cylindrical member <b>18</b> that is installed in outer cylindrical member <b>17</b> to receive a torque from input shaft <b>2</b>, a plurality of balls <b>20</b> that are rotatably disposed between the two cylindrical members <b>17</b> and <b>18</b> to serve as a torque transmitting means and a circular cage <b>19</b> that rotatably holds balls <b>20</b>.

p-0034As is seen from <figref idrefs="DRAWINGS">FIG. 2</figref>, outer cylindrical member <b>17</b> is shaped like a cup and formed at its outer cylindrical surface with an annular groove <b>17</b><i>a</i>. An inner surface <b>17</b><i>b </i>of outer cylindrical member <b>17</b> is shaped concave so that outer cylindrical member <b>17</b> is pivotal about a unit of balls <b>20</b>. A smaller diameter right end portion <b>17</b><i>c </i>of outer cylindrical member <b>17</b> is tightly connected to a left end of drive shaft <b>4</b>.

p-0035Within smaller diameter right end portion <b>17</b><i>c </i>of outer cylindrical member <b>17</b>, there is press-fitted a circular seal cap <b>22</b>, and between a larger diameter front end <b>17</b><i>d </i>of outer cylindrical member <b>17</b> and an after-mentioned sleeve member <b>21</b> which is tightly connected to inner cylindrical member <b>18</b>, there is arranged an annular boot unit <b>23</b>.

p-0036Inner cylindrical member <b>18</b> is made of a steel or the like and formed with a center through bore <b>18</b><i>a </i>into which the above mentioned smaller diameter right shaft portion <b>13</b> of input shaft <b>2</b> is inserted.

p-0037Center through bore <b>18</b><i>a </i>and right shaft portion <b>13</b> are connected through a spline coupling. For this spline coupling, center through bore <b>18</b><i>a </i>has a plurality of splines <b>24</b> and the right shaft portion <b>13</b> of input shaft <b>2</b> has a plurality of splines <b>15</b>.

p-0038Inner cylindrical member <b>18</b> has a convex outer surface <b>18</b><i>b </i>on which balls <b>20</b> roll. The splined inner cylindrical wall <b>24</b> of center through bore <b>18</b><i>a </i>is, at a position near a right end thereof, with an annular groove <b>25</b> into which the above-mentioned snap ring <b>16</b> is tightly received upon proper coupling between input shaft <b>2</b> and the universal joint <b>3</b><i>a. </i>

p-0039As is seen from <figref idrefs="DRAWINGS">FIG. 1</figref>, sleeve member <b>21</b> is made of a steel and press-fitted to a left end of inner cylindrical member <b>18</b>, so that sleeve member <b>21</b> and inner cylindrical member <b>18</b> move together like a single unit. For this press-fitting, inner cylindrical member <b>18</b> is formed with an annular groove <b>26</b> for tightly receiving therein the right end of sleeve member <b>21</b>, as shown.

p-0040If desired, sleeve member <b>21</b> may be integral with inner cylindrical member <b>18</b>.

p-0041As is seen from <b>3</b>, annular groove <b>25</b> is shaped to have a generally trapezoidal cross section. A depth “d” of annular groove <b>25</b> to a bottom wall <b>25</b><i>a </i>is determined about ⅖ of the diameter of snap ring <b>16</b>. As shown, a right side wall <b>25</b><i>b </i>of annular groove <b>25</b> is perpendicular (viz., β=90 degrees) to bottom wall <b>25</b><i>a </i>and a left side wall <b>25</b><i>c </i>of annular groove <b>25</b> is inclined about 50 degrees (viz., α=50 degrees) relative to bottom wall <b>25</b><i>a. </i>

p-0042Accordingly, if a certain force is applied to input shaft <b>2</b> in a direction of the arrow “F” causing a leftward movement of the right shaft portion <b>13</b> and abutment of snap ring <b>16</b> with the inclined left side wall <b>25</b><i>c </i>of annular groove <b>25</b>, snap ring <b>16</b> is forced to reduce its diameter permitting disengagement of input shaft <b>2</b> from inner cylindrical member <b>18</b>, particularly from the splined center through bore <b>18</b><i>a. </i>

p-0043It is thus to be noted that annular groove <b>13</b><i>b </i>of input shaft <b>2</b>, snap ring <b>16</b> and annular groove <b>25</b> of inner cylindrical member <b>18</b> constitute a positioning mechanism through which input shaft <b>2</b> can be axially positioned relative to first constant velocity universal joint <b>3</b><i>a. </i>

p-0044As is seen from <figref idrefs="DRAWINGS">FIG. 1</figref>, a left end <b>21</b><i>d </i>of a smoothed inner cylindrical wall <b>21</b><i>c </i>of sleeve member <b>21</b> is tapered to facilitate the work for inserting smaller diameter right shaft portion <b>13</b> into sleeve member <b>21</b>.

p-0045As is seen from <figref idrefs="DRAWINGS">FIG. 2</figref>, when the right portion of input shaft <b>2</b> is properly and sufficiently led into sleeve member <b>21</b>, snap ring <b>16</b> caught by annular groove <b>13</b><i>b </i>becomes engaged with annular groove <b>25</b> of the inner cylindrical wall of inner cylindrical member <b>18</b>. Upon this, positioning of input shaft <b>2</b> relative to inner cylindrical member <b>18</b> is achieved while forming a thin space “C<b>1</b>” between annular flat surface <b>11</b><i>a </i>of input shaft <b>2</b> and the left end part of sleeve member <b>21</b>, as shown. It is to be noted that the space “C<b>1</b>” is used for putting therein a tip of a special pick (not shown) at the time when it is needed to disengage the right end portion of input shaft <b>2</b> from sleeve member <b>21</b>.

p-0046The above-mentioned annular boot unit <b>23</b> comprises an annular metal retainer <b>27</b> that has a right end fixed to outer cylindrical member <b>17</b>, an annular boot <b>28</b> that has a larger diameter outer peripheral portion <b>28</b><i>a </i>fixed to a left end of annular metal retainer <b>27</b> and a fastening band <b>29</b> that is arranged to bind a smaller diameter inner peripheral portion <b>28</b><i>b </i>of annular boot <b>28</b> to sleeve member <b>21</b>, as shown.

p-0047More specifically, as is seen from <figref idrefs="DRAWINGS">FIGS. 1 and 2</figref>, annular metal retainer <b>27</b> is a stepped member comprising a rightmost base portion <b>27</b><i>a </i>that is tightly disposed in an annular groove <b>17</b><i>a </i>formed on outer cylindrical member <b>17</b> and a leftmost curled end <b>27</b><i>b </i>that tightly catches larger diameter end portion <b>28</b><i>a </i>of annular boot <b>28</b>.

p-0048Annular boot <b>28</b> is made of a rubber or plastic material and constructed to have a generally U-shaped cross section. As shown, when assembled, annular boot <b>28</b> is so oriented as to project its swelled portion toward balls <b>20</b>.

p-0049Smaller diameter end portion <b>28</b><i>b </i>of annular boot <b>28</b> is formed with both an inner annular ridge (no numeral) that is tightly received in an annular groove <b>21</b><i>b </i>formed on sleeve member <b>21</b> and an outer annular groove <b>28</b><i>d </i>that tightly receives the above-mentioned annular band <b>29</b>.

p-0050Due to provision of annular boot unit <b>23</b> and circular seal cap <b>22</b>, a grease can be held in a space defined between outer and inner cylindrical members <b>17</b> and <b>18</b>.

p-0051Although first constant velocity universal joint <b>3</b><i>a </i>is of a fixed type, it allows a slight swinging between input shaft <b>2</b> and drive shaft <b>4</b>. Second constant velocity universal joint <b>5</b> (see <figref idrefs="DRAWINGS">FIG. 4</figref>) is constructed to permit a relative movement thereof in an axial direction. Thus, the work for assembling propeller shaft <b>1</b><i>a </i>to the vehicle body is facilitated.

p-0052Third constant velocity universal joint <b>7</b> is substantially the same as the above-mentioned first constant velocity universal joint <b>3</b><i>a</i>, and thus description on the construction of the joint <b>7</b> will be omitted.

p-0053In the following, assembling steps for propeller shaft la and operation of first constant velocity universal joint <b>3</b><i>a </i>will be described with the aid of the drawings.

p-0054First, the work for assembling annular boot unit <b>23</b> will be described. That is, in a component factory, by using a common method, larger diameter outer peripheral portion <b>28</b><i>a </i>of annular boot <b>28</b> is connected to annular metal retainer <b>27</b> in the above-mentioned manner. Then, the base portion <b>27</b><i>a </i>of metal retainer <b>27</b> is tightly received in annular groove <b>17</b><i>a </i>of outer cylindrical member <b>17</b>.

p-0055Then, smaller diameter inner peripheral portion <b>28</b><i>b </i>of annular boot <b>28</b> is disposed on the left end of sleeve member <b>21</b> and fastening band <b>29</b> is disposed on smaller diameter inner peripheral portion <b>28</b><i>b </i>of annular boot <b>28</b>, and fastening band <b>29</b> is tightened in a known manner. With this, annular boot unit <b>23</b> is properly mounted to first constant velocity universal joint <b>3</b><i>a. </i>

p-0056In a vehicle body assembling factory, first constant velocity universal joint <b>3</b><i>a </i>and input shaft <b>11</b> are combined in the following manner.

p-0057That is, as is seen from <figref idrefs="DRAWINGS">FIGS. 1 and 2</figref>, the right shaft portion <b>13</b> of input shaft <b>2</b> is inserted into sleeve member <b>21</b> and then into center through bore <b>18</b><i>a </i>of inner cylindrical member <b>18</b>. During this insertion, snap ring <b>16</b> resiliently disposed in annular groove <b>13</b><i>b </i>formed on the right shaft portion <b>13</b> is forced to slide on and along smoothed inner cylindrical wall <b>21</b><i>c </i>of sleeve member <b>21</b> and then on and along the splined inner cylindrical wall <b>24</b> of inner cylindrical member <b>18</b> while being compressed in a direction to reduce its diameter. At a latter stage of this insertion, engagement between splines <b>15</b> and <b>24</b> is deeply made while receiving a counter force.

p-0058Under this sliding, snap ring <b>16</b> is kept compressed while pressing its outer portion against the splined inner cylindrical wall <b>24</b>.

p-0059However, as is seen from <figref idrefs="DRAWINGS">FIG. 2</figref>, when, after travelling in sleeve member <b>21</b> and inner cylindrical member <b>18</b>, the right shaft portion <b>13</b> comes to its rightmost position, snap ring <b>16</b> is permitted to expand radially outward and engaged with annular groove <b>25</b>. Upon this, stable connection between input shaft <b>2</b> and first constant velocity universal joint <b>3</b><i>a </i>is established. It is to be noted that as is seen from <figref idrefs="DRAWINGS">FIG. 3</figref>, under this engaged condition, snap ring <b>16</b> is kept compressed having its outer peripheral part pressed against bottom wall <b>25</b><i>a </i>of annular groove <b>25</b>.

p-0060With the above-mentioned assembling steps, input shaft <b>2</b> and first constant velocity universal joint <b>3</b><i>a </i>are coupled together with the aid of the spline coupling effected by splines <b>15</b> and <b>24</b> and with the resilient engagement of snap ring <b>16</b> with annular groove <b>25</b>. Of course, under this condition, unexpected disengagement of input shaft <b>2</b> from the universal joint <b>3</b><i>a </i>is suppressed.

p-0061That is, input shaft <b>2</b> and the universal joint <b>3</b><i>a </i>are operatively connected through the engagement between splines <b>15</b> and <b>24</b> and the engagement between snap ring <b>16</b> and annular groove <b>25</b>. In other words, in the first embodiment of the invention, for operatively connecting input shaft <b>2</b> and the universal joint <b>3</b><i>a</i>, no bolts are used. That is, in this first embodiment, a torque transmission from input shaft <b>2</b> to drive shaft <b>4</b> is assuredly carried out without usage of any connecting bolts.

p-0062When smaller diameter right shaft portion <b>13</b> is sufficiently inserted into inner cylindrical member <b>18</b>, snap ring <b>16</b> is brought into engagement with annular groove <b>25</b>. Upon this, further axial movement of the right shaft portion <b>13</b> relative to inner cylindrical member <b>18</b> and thus relative to outer cylindrical member <b>17</b> is suppressed. That is, upon assembling, axial positioning of the right shaft portion <b>13</b> of input shaft <b>2</b> relative to outer cylindrical member <b>17</b> is assured.

p-0063As will be understood from the foregoing description, the engagement of snap ring <b>16</b> with annular groove <b>25</b> is effected by simply pushing input shaft <b>2</b> into inner cylindrical member <b>18</b>. That is, the work for properly connecting input shaft <b>2</b> to the universal joint <b>3</b><i>a </i>is very easy.

p-0064As is seen from <figref idrefs="DRAWINGS">FIG. 2</figref>, under the condition wherein input shaft <b>2</b> is deeply or properly inserted into inner cylindrical member <b>18</b>, seal ring <b>14</b> on medium diameter intermediate portion <b>12</b> is pressed against the smoothed inner cylindrical wall of sleeve member <b>21</b>, and thus, the interior of outer cylindrical member <b>17</b> is protected from the entry of muddy water, dusts or the like. Of course, due to provision of seal ring <b>14</b>, leakage of the grease from the interior of outer cylindrical member <b>17</b> is suppressed.

p-0065Furthermore, since seal ring <b>14</b> is tightly held by annular groove <b>12</b><i>a </i>of the cylindrical outer surface of the intermediate portion <b>12</b> and arranged to seal an entirely outer surface of the intermediate portion <b>12</b> for its sealing area, seal ring <b>14</b> can exhibit a satisfied sealing performance.

p-0066Furthermore, since snap ring <b>16</b> is placed in the interior of outer cylindrical member <b>17</b> while keeping away from seal ring <b>14</b>, snap ring <b>16</b> is sufficiently fed with the grease from the interior of outer cylindrical member <b>17</b>, which suppresses corrosion of snap ring <b>16</b>.

p-0067As is described hereinabove, in this first embodiment, the connection between input shaft <b>2</b> and first constant velocity universal joint <b>3</b><i>a </i>is made through the engagement between splines <b>15</b> and <b>24</b> and the catching or holding function of snap ring <b>16</b> without usage of conventional bolts. Accordingly, in this embodiment, reduction in component count is delivered and thus weight reduction of propeller shaft <b>1</b><i>a </i>and efficient assembly operations for vehicles are achieved. Furthermore, because of presence of seal ring <b>14</b>, the above-mentioned dust-tight and grease holding performance is obtained.

p-0068Furthermore, as will be understood from <figref idrefs="DRAWINGS">FIG. 1</figref>, due to provision of tapered end <b>13</b><i>a </i>of smaller diameter shaft portion <b>13</b> and the tapered peripheral inner edge <b>21</b><i>d </i>of sleeve member <b>21</b>, the shaft portion <b>13</b> of input shaft <b>2</b> can be easily guided into sleeve member <b>21</b> of the universal joint <b>3</b><i>a</i>, which brings about an easy and instant coupling between input shaft <b>2</b> and the joint <b>3</b><i>a. </i>

p-0069As will be understood from <figref idrefs="DRAWINGS">FIG. 2</figref>, when it is needed to disengage input shaft <b>2</b> from the universal joint <b>3</b><i>a</i>, a special pick (not shown) is handled to put its tip into the thin space “C<b>1</b>” provided between annular flat surface <b>11</b><i>a </i>of input shaft <b>2</b> and the left end of sleeve member <b>21</b> and then the pick is pivoted in a certain direction using an outer end of annular flat surface <b>11</b><i>a </i>as a fulcrum. With these steps, input shaft <b>2</b> is displaced leftward in the direction of “F” in <figref idrefs="DRAWINGS">FIG. 3</figref> together with snap ring <b>16</b>.

p-0070Due to this leftward movement, snap ring <b>16</b> is brought into abutment with the inclined left side wall <b>24</b><i>c </i>of annular groove <b>25</b> and thus thereafter, the diameter of snap ring <b>16</b> is gradually reduced as snap ring <b>16</b> slides down on and along the inclined left side wall <b>25</b><i>c </i>in accordance with the leftward movement of input shaft <b>2</b>. Once the leftward movement comes to a certain level, the diameter of snap ring <b>16</b> becomes sufficiently small to unlock the engagement between input shaft <b>2</b> and sleeve member <b>21</b>, and thus, thereafter, input shaft <b>2</b> is instantly disengaged from first constant velocity universal joint <b>3</b><i>a. </i>

p-0071Referring to <figref idrefs="DRAWINGS">FIG. 5</figref>, there is shown a front assembly of a propeller shaft <b>1</b><i>b </i>which is a second embodiment of the present invention.

p-0072Since this second embodiment is similar to the above-mentioned first embodiment, only parts or portions that are different from those of the first embodiment will be described in the following.

p-0073As is seen from <figref idrefs="DRAWINGS">FIG. 5</figref>, in this second embodiment, in addition to annular groove <b>12</b><i>a</i>, another annular groove (viz., second annular groove) <b>12</b><i>b </i>is provided by medium diameter intermediate portion <b>12</b> of input shaft <b>2</b>. A second seal ring <b>29</b> is tightly held by second annular groove <b>12</b><i>b</i>. Like the seal ring <b>14</b>, second seal ring <b>29</b> is pressed against the smoothed cylindrical inner surface of sleeve member <b>21</b>.

p-0074Because of usage of two seal rings <b>14</b> and <b>29</b>, much effective sealing against muddy water, dusts or the like is obtained in this embodiment. Furthermore, due to provision of such two seal rings <b>14</b> and <b>29</b>, undesired leakage of the grease from the interior of outer cylindrical member <b>17</b> to the outside is much assuredly suppressed.

p-0075Referring to <figref idrefs="DRAWINGS">FIG. 6</figref>, there is shown a front assembly of a propeller shaft <b>1</b><i>c </i>which is a third embodiment of the present invention.

p-0076In this third embodiment, the axial length of medium diameter intermediate portion <b>12</b> of input shaft <b>2</b> is small as compared with those of the above-mentioned first and second embodiments.

p-0077Furthermore, in this third embodiment, a seal ring <b>31</b> is tightly received in an annular groove <b>30</b> that is formed on the smoothed inner cylindrical wall of sleeve member <b>21</b>. In use, seal ring <b>31</b> is pressed against the cylindrical outer surface of medium diameter intermediate portion <b>12</b> of input shaft <b>2</b>.

p-0078Referring to <figref idrefs="DRAWINGS">FIG. 7</figref>, there is shown a front assembly of a propeller shaft id which is a fourth embodiment of the present invention.

p-0079In this fourth embodiment, an annular groove <b>32</b> is formed on and around a root portion of medium diameter intermediate portion <b>12</b> of input shaft <b>2</b>, and a seal ring <b>33</b> is tightly received in annular groove <b>32</b>. That is, when the right shaft portion <b>13</b> of input shaft <b>2</b> is properly set in inner cylindrical member <b>18</b>, seal ring <b>33</b> is compressed between annular flat surface <b>11</b><i>a </i>of input shaft <b>2</b> and the tapered left end <b>21</b><i>d </i>of sleeve member <b>21</b>, as shown.

p-0080With provision of seal ring <b>33</b>, the clearance “C<b>1</b>” is directly sealed, and thus the interior of outer cylindrical member <b>17</b> is protected from the entry of muddy water, dusts or the like.

p-0081Referring to <figref idrefs="DRAWINGS">FIG. 8</figref>, there is shown a front assembly of a to propeller shaft <b>1</b><i>e </i>which is a fifth embodiment of the present invention.

p-0082In this fifth embodiment, an annular groove <b>34</b> is formed on annular flat surface <b>11</b><i>a </i>of input shaft and a seal ring <b>35</b> is tightly received in annular groove <b>34</b>. That is, when the right shaft portion <b>13</b> of input shaft <b>2</b> is properly set in inner cylindrical member <b>18</b>, seal ring <b>35</b> is compressed between a bottom wall of annular groove <b>34</b> and the left end of sleeve member <b>21</b>, as shown.

p-0083Like in the above-mentioned fourth embodiment, the clearance “C<b>1</b>” is directly sealed, and thus, the interior of outer cylindrical member <b>17</b> is protected from the entry of muddy water, dusts or the like.

p-0084Referring to <figref idrefs="DRAWINGS">FIG. 9</figref>, there is shown a front assembly of a propeller shaft if which is a sixth embodiment of the present invention.

p-0085In this sixth embodiment, the axial length of the smaller diameter right shaft portion <b>13</b> of input shaft <b>2</b> is longer than those of the above-mentioned embodiments. Thus, annular groove <b>25</b> used for limiting the axial movement of the right shaft portion <b>13</b> is placed at the right end of the center through bore <b>18</b><i>a </i>of inner cylindrical member <b>18</b>.

p-0086Due to the longer construction of the right shaft portion <b>13</b>, the mechanical strength of the portion <b>13</b> is increased and the engagement between splines <b>15</b> and <b>24</b> is much effectively made.

p-0087The entire contents of Japanese Patent Application 2012-66120 filed Mar. 22, 2012 are incorporated herein by reference.

p-0088Although the invention has been described above with reference to the embodiments of the invention, the invention is not limited to such embodiments as described above. Various modifications and variations of such embodiments may be carried out by those skilled in the art, in light of the above description.